Isn't the outcome the same, if passive is the floor? It seems like your choice on that is cornering you into modifying the feat.Personally, I use a couple of houserules to avoid some of these issues.
First, I let Observant give advantage on active Perception and Investigation checks, in addition to passive checks. I do this because I don't want the utility of the feat to depend heavily on whether I call for an active check or use a passive check. (As a general principle, I don't want the outcome of an in-game action to be dependent on the choice between two different resolution methods.)
Are you saying here - we don't want some traps that need Investigation, and some that do not? If so, that was the kind of consideration that just lead me to say it is consistently Investigation for artifacts.Second, in addition to deduction, I let Investigation also apply to situations covered by the old Gather Information skill, and I also let it work as a general-purpose Research skill (broader than just finding hidden fragments of knowledge). I find this gives the Investigation skill enough alternative uses that I don't have to go out of my way to design traps and other game elements in a way that makes Investigation useful--instead I can just design traps with the builder's IC goals/resources in mind.
A bad way to rule in my view is where Perception lets a character notice say some fine seams in the wall, but they would still need their Investigation to know they signified a secret door and how to open it. Either compounding the difficulty, or halving it, depending on if both must succeed, or success with either does the work. After many sessions I landed on just saying - it's Investigation for an architectural feature like a secret door because even if you did notice the seams, it was still going to use that skill at some point. I suppose one imagines the character noticing there is an inexplicable void between rooms, and putting that together with other suspicious features... or whatever.
My starting point was more as some other posters rule... but it just created inconsistencies for me in play. It's interesting how often I come back to consistency as a measure of a good ruling.